I guess I can't say this enough times, but I agree that the terrorists are going to make future attempts against us.In sum, however, those attempts will do less to the U.S. than they have done to Israel (where Palestinians almost outnumber Jews).
Yes, if they still have Anthrax they will use it here, however, anthrax makes for a lousy weapon. For one thing, it isn't always fatal. For another, it's never instantly fatal. Hit a platoon with anthrax and they'll live to shoot you dead, and then they'll all go get hopped up on some major antibodies and most of them will survive the whole ordeal unscathed.
Look at the cruise ship attacks. The disease that is being spread on those cruise ships could easily be fatal, except that it is treatable and cureable with our advanced medicine.
And we've had what, some 25 more train derailments than normal since 9/11/01?? Big deal.
They've done what, take down one more jet (oops, I meant, the tail fell off by accident), and then fire some rockets at an Israeli aircraft in Africa? Again, pretty minor in the grand scheme of things.
They'll probably cook off a couple of their diehards in order to draw blood in a more public way, but such things are pretty trivial overall.
For instance, I talked to a life insurance muckity muck after 9/11 to ask how big of an impact it was going to have on his company. He explained, "we get 12,000 deaths per day in the U.S. on average, so 9/11/01 was only a 15,000 death day" for his industry, something that they shrugged off without even having to note on their 10K's as a material event.
We can handle whatever it is that the terrorists try to dish out.
The converse, however, is not true for them. They can't handle it if we unleash our nukes and erase the Middle-East. They can't handle it if we unleash our biological warfare agents and wipe out Africa and Asia. they can't handle it if we unleash our chemical and nerve agents to depopulate entire regions. Heck, they can't even stop our conventional military from going where ever we want to go, bombing whoever we want to bomb, occupying whatever we want to occupy, etc., etc., etc...